Portable Game Notation (PGN) is a plain text
computer-processible
format for recording chess games (both the moves and related data),
supported by many chess programs.

History

PGN was devised around 1993, by Steven J. Edwards, and was
first popularized via the Usenet newsgroup rec.games.chess.

Usage

PGN is structured "for easy reading and writing by human users
and for easy parsing and generation by computer programs." The chess
moves themselves are given in algebraic chess notation. The usual
filename extension is ".pgn".
There are two formats in the PGN specification, the "import" format and
the "export" format. The import format describes data that may have
been prepared by hand, and is intentionally lax; a program that can
read PGN data should be able to handle the somewhat lax import format.
The export format is rather strict and describes data prepared under
program control, similar to a pretty printed source program reformatted
by a compiler. The export format representations generated by different
programs on the same computer should be exactly equivalent, byte for
byte.
PGN code begins with a set of "tag pairs" (a tag name and its value),
followed by the "movetext" (chess moves with optional commentary).

Tag pairs

Tag pairs begin with an initial left bracket "[", followed by
the name of the tag in plain text (ASCII). The tag value is enclosed in
double-quotes, and the tag is then terminated with a closing right
bracket "]". There are no special control codes involving escape
characters, or carriage returns and linefeeds to separate the fields,
and superfluous embedded spaces (or SPC characters) are usually skipped
when parsing.
PGN data for archival storage is required to provide seven bracketed
fields, referred to as "tags" and together known as the STR (Seven Tag
Roster). In export format, the STR tag pairs must appear before any
other tag pairs that may appear, and in this order:

Event: the name of the tournament or match event.

Site: the location of the event. This is in "City, Region
COUNTRY" format, where COUNTRY is the three-letter International
Olympic Committee code for the country. An example is "New York City,
NY USA".

Date: the starting date of the game, in YYYY.MM.DD form.
"??" are used for unknown values.

Round: the playing round ordinal of the game within the
event.

White: the player of the white pieces, in "last name, first
name" format.

Black: the player of the black pieces, same format as White.

EResult: the result of the game. This can only have four
possible values: "1-0" (White won), "0-1" (Black won), "1/2-1/2"
(Draw), or "*" (other, e.g., the game is ongoing).

The standard allows for supplementation in the form of other,
optional, tag pairs. The more common tag pairs include:

Annotator: The person providing notes to the game.

PlyCount: String value denoting total number of half-moves
played.

TimeControl: "40/7200:3600" (moves per seconds: sudden
death seconds)

Time: Time the game started, in "HH:MM:SS" format, in local
clock time.

Termination: Gives more details about the termination of
the game. It may be "abandoned", "adjudication" (result determined by
third-party adjudication), "death", "emergency", "normal", "rules
infraction", "time forfeit", or "unterminated".

Mode: "OTB" (over-the-board) "ICS" (Internet Chess Server)

FEN: The initial position of the chess board, in
Forsyth-Edwards Notation. This is used to record partial games
(starting at some initial position). It is also necessary for chess
variants such as Fischer random chess, where the initial position is
not always the same as traditional chess. If a FEN tag is used, a
separate tag pair "SetUp" must also appear and have its value set to
"1".

Movetext

The
movetext describes the actual moves of the game. This includes move
number indicators (numbers followed by either one or three periods; one
if the next move is White's move, three if the next move is Black's
move) and movetext Standard Algebraic Notation (SAN).
For most moves the SAN consists of the letter abbreviation for the
piece, an "x" if there is a capture, and the two-character algebraic
name of the final square the piece moved to. The letter abbreviations
are "K" (king), "Q" (queen), "R" (rook), "B" (bishop), and "N"
(knight). The pawn is given an empty abbreviation in SAN movetext, but
in other contexts the abbreviation "P" is used. The algebraic name of
any square is as per usual Algebraic chess notation; from white's
perspective, the leftmost square closest to white is a1, the rightmost
square closest to the white is h1, and the rightmost (from white's
perspective) square closest to black side is h8.
In a few cases a more detailed representation is needed to resolve
ambiguity; if so, the piece's file letter, numerical rank, or the exact
square is inserted after the moving piece's name (in that order of
preference). Thus, "Nge2" specifies that the knight originally on the
g-file moves to e2.
SAN kingside castling is indicated by the sequence "O-O"; queenside
castling is indicated by the sequence "O-O-O" (note that these are
capital letter "O"s, not numeral "0"s). Pawn promotions are notated by
appending an "=" to the destination square, followed by the piece the
pawn is promoted to. For example: "e8=Q". If the move is a checking
move, the plus sign "+" is also appended; if the move is a checkmating
move, the number sign "#" is appended instead. For example: "e8=Q#".
An annotator who wishes to suggest alternative moves to those actually
played in the game may insert variations enclosed in parentheses. He
may also comment on the game by inserting Numeric Annotation Glyphs
(NAGs) into the movetext. Each NAG reflects a subjective impression of
the move preceding the NAG or of the resultant position.
If the game result is anything other than "*", the result is repeated
at the end of the movetext.

Comments

Comments are inserted by either a ";" (a comment that
continues to the end of the line) or a "{" (which continues until a
matching "}"). Comments do not nest.

Handling chess variants

Many chess variants can be recorded using PGN, provided the
names of the pieces can be limited to one character, usually a letter
and not a number. They are typically noted with a tag named "Variant"
giving the name of the rules. The term "Variation" must be avoided, as
that refers to the name of an opening variation. Note that traditional
chess programs can only handle, at most, a few variants.
Forsyth-Edwards Notation (FEN) is used to record the starting position
for variants (such as Chess960) which have initial positions other than
the orthodox chess initial position.
Plycount is a chess term for the total number of moves in a game,
counting each player's move as one. It is an optional part of the
standard PGN description of a chess game.